Selective switch



March 8, 1938. w. w. cARPa-NTER Er AL .2, 1l0460 SELECTIVE SWITCH n. n? CARPENTER NVEVO J. N. REV/vows' A T TORNEV FIG. .2

March 8, 1938. w. w. CARPENTER ET A1. l 2,110,450

SELECTIVE SWITCH Filed Sept. 25, 1935 5 Sheets-Sheet 2 CONNECTOR Seco/MARY sW/TcHS PR/MARV SW/TCHES w n. cARP/vrE/P /NvENToRs J N REy/VOLDS ATTO@ EY SELECT-IVE SWITCH Filed spt. 25, 195s 5 sheets-sheet 3 M M- uw A MH w M1. m I l n M .w1 M f D- -1 1 Mn uw MH J m m m l@ n. .1.- .u .1- m M m 4 1 a Q 4 @TMN- P uw @QM @EN W1 k W w D- dun. .D H A n w g/VENTORS w w CARPENTER By J. N. REYNOLDS A TTOR/VEV Patented Mar. 8, 1938 UNiTED STATES PATENT OFFICE SELECTIVE SWITCH Application September 25, 1936, Serial No. 102,454

9 Claims.

This invention relates yto the construction and operation of selective switches and to the controlling equipment therefor and particularly to switches of the class used for the establishment of connections in telephone systems.

The objects of the invention are to increase the operating speed of selective switches; to simplify the circuits used for controlling the operation of these switches; and to effect other improvements in equipment of this character.

In automatic telephone systems of the prior art in which switches of the cross-bar type are used it has been the usual practice to provide a circuit controlling means fordetermining the particular switch through which the desired connection is to be extended and then for operating the cross-bars of the switch to establish the connection. More recently it has been found that in systems of large capacity a more eicient use of the cross-bar switch can be realized by arranging the switches in a primary and secondary relation at the successive stages and interconnecting these stages with link circuits. Since the testing of the successive links comprising the paths through these stages requires a very brief interval of time, the best results are obtained by allowing the common controlling and testing mechanism to have exclusive use of an entire frame of switches while it is testing links and establishing a connection therethrough. This makes it possible for the testing mechanism to examine all possible link paths through a stage, each of which leads through a different cross-bar switch at each portion of the stage, in an elort to find at least one idle path. With this arrangement any one of ten equivalent switches on a framemay have a link circuit that could serve the particular connection involved providedthis link can be matched with a link preceding it and also with a link succeeding it in the path. At the time the controlling mechanism seizes the frame it is not known which one of the switches will ultimately take part in the connection. For these reasons it is highly desirable from the standpoint of circuit operation to have all of the switches prepared in advance so that the operation of the lone finally chosen for use can be completed without delay. y

' Accordingly a feature of the present invention is a system in which a selective switching stage includes a plurality of separate cross-bar switches `for effecting connections between incoming and `outgoing circuits and in which the bars on a plurality of switches arecperated simultaneously by a single common operating device to cause the establishment of a desired connection through some one of the switches at the switching stage. As soon as the connection has been extended through a particular one of the switches, the operating device is permitted to release and restore the operated bars on the several switches in readiness for the next call through the stage. To illustrate this feature more explicitly, it may be considered that a stageincludes ten cross-bar switches, each having ten rows of contacts accommodating ten incoming circuits and ten outgoing circuits, and each switch having five select bars, each bar serving two rows of contacts, or two of the outgoing circuits. If now a given group of ten outgoing circuits is so distributed over the ten switches that each switch has one circuit, then it will be possble for any given call for said group to be completed over any one of the ten switches. And the switch iinally chosen to complete the call is determined by the busy or idle condition of the circuits incoming to the switches as well as the condition of the circuits of the desired outgoing group. Y Since the said desired outgoing group is known before the tests for idle circuits are completed, it is expedient to prepare all switches having access to the group. And this is done as above explained by means of a common operating device which sets at once the ten select bars which are individual in the respective ten switches to the correspondingten circuits of the outgoing group. As soon as the particular circuit to be used is determined, the hold bar of the switch in which it appears is operated to eifect the connection, and all of the operated select bars are released. In a similar manner the remaining four sets of ten select bars, each of which sets includes a bar in each of the ten switches, are operated respectively by four common operating devices in connection with calls to other groups of outgoing circuits.

A related feature of the invention is a stage of switches in which a single bar in each switch controls selection of two outgoing circuits, and in which the bars in a plurality of switches are provided with a common actuating mechanism which operates all of them simultaneously either in one direction or another according to the circuits desired.

These and other features of the invention will be described mor-efully in the following detailed specification.

In the drawings which accompany the specification:

Figs. l, 2 and 3, when arranged as shown in Fig. 4, illustrate in diagrammatic form a portion of the equipment at a switching stage in anY automatic telephone system, together with certain parts of the switch controlling equipment; n

Fig. 1 shows a number of trunks incoming to a district selector frame and also a number of the primary and secondary district switches;

Fig. 2 shows a number of primary and secondary selectors of an oflice frame accessible to the district frame ofFig. 1, together with a number ,of groups of trunks outgoing VVfromY the office frame; and Y Fig. 3 discloses parts of a marker for control-Y ling the switches of the district and oiice frames.

The purpose of the selective switching stage comprising the district switches of Fig. 1 andV the ,oice switches of Fig. 2 is to establish connections between the incoming district trunks, i

which have been seized by subscribers lines, andy an idle Vtrunkin any one Vof a number of Voutgoing groups, as determined by the oflice code of the designation dialed `by the subscriber. lThe district selectors are arranged in frames of primary switches and frames Vof secondary switches. A frame of primary switches maycomprise ten cross-bar switches, -of which three, switches PD-Il, PD--land- PD--9, are illustrated in the drawings. Each of'these primary district crossbar switches, and the same is truerof the other cross-bar switches disclosed in the drawings; has ten horizontal rows of contactsand ten vertical rows of contacts. The incoming district trunks Vappear in the horizontal rows of contacts Yof these switches, there being ten groups of ten Vor'one hundred district trunks appearing ina district frame. In the drawings threeof these groupsof district trunks, |00, IUI, and H32, are illustrated. There are alsorten secondary switches on the district selector frame,` three of which, S13-Il, SD-r-I, and SID-9, are shown. The primary and secondary district switches are interconnected by links `which appearin the vertical rows ofecentacts inthe primary switchesjand in the horizontal rows of contacts in the secondaryV switches, as illustrated in Fig'. 1. j

vIn a similar manner each of thefoflice frames comprises'ten primary oiliee switches, including and appear in the horizontalrows of'contactsof Ythe oilice secondary selector switches. For simplicity only three `of these outgoing trunk groups are illustrated.- One of these groups, corn;- prising ten trunks is illustratedeby, the `three trunks |03,k |04, and Iil5; Trunk ID3 appearsVv in the zero' horizontal row of switch rSO--ll, 'andYV trunksIM andIIlS similarlyappea'r in'the zero horizontalrows of switches SO-dzand Y'SO-Sl. In a similar manner the other seven rtrunks of the same group appear'in the zero'l'evels of the corresponding secondary oice selector switches.

lAnother groupY of trunks is represented bythe three trunks Ing, 101, andul08 appearing inthe No. 4 horizontal levelsyof ,the secondary ofiice' contacts of the corresponding secondary oiiice switches. Since each of the secondary oilice selector switches has ten horizontal rows of cono tacts, there may be as many as ten groups of outgoing trunks.

The'district'links interconnect the primary and secondary district switches in such manner that access may be had through any one of the ten district primary switches to any one of the ten district secondary switches. For example, the ten district links II2, which occupy the ten vertical rows. of contacts in the primary switch PD-Ilg, extend respectively and appear in the zero horizontal ,rows of the ten secondary switches SD-D to SD-9. Likewise the ten district links II3 extend from thedistrict primary switch PD-4 to theNo. 4 horizontal rows of the respective secondary switches SD-D to 'SD-9. Similarly the ten district linksV I I4 extend from the primaryv switch PD-`9 to the No. 9 horizontal rows'of` contacts of the ten secondary switches. AndV the same is true of the remaining seven groups of district links not shown. The links or oi'lice trunks interconnecting the district and oflice frames are divided into groups, each district Vframe having ten groups of trunks extendingnto ten respective oflice frames. r drawings one of these groups, including omce trunks H5, IIB and III, is illustrated. 'Ihe ten trunks, including trunks II5, IIS-and IVI1, appear Y respectively in the No. 0 vertical rows of co'ntacts of the ten secondary district switches. 'I'hesetrunks extend to the oflice frame shown in Fig. .2' and Vthere appear respectively inthe No( 0? vertical'rows of the ten oiice primary switches PO-Uf'to PO-Sj In a similar manner the remaining nine groups of district trunks outgoing from the district'frame shown in Fig. 1 ex v tendV to nine other ofceframes and appear in Vthe respective vertical rows of the Vprimary o iiice switches. The oilice links, which interconnect Vthe primary oice switches and the secondary oice switches, Vare so arranged that any one of the ten primary office switches has access to anyone of the ten secondary switches. For example, the ten office links IIB; which appear in the primary oflice switch PO-0, are distributed and appear in the No. 0 vertical rows In' the of the respective secondary Voilice switches SO--Il Y ,to'VSO-V-S. In like manner the groups of oflice links IIS and i120 each appearing respectively in switches PrO-4 and PO-Sare distributed among the ten secondary switches VSO---Il to SO-9 and the same is true of the remaining groups of Yofrnce links, not shown. o

The cross-bar switchesV illustrated diagrammatically herein maybe of kany well-known and suitable 'type such as the one disclosed in the Y patentto Reynolds 41,139,722 of May 18,v 1915. As

illustrated, however, the' switches disclosed herein differ from the one in the Reynolds patent in that the horizontal orselect bars are'rotatable in VVboth directions so that each bar serves two hori- Y zontal rows of contacts., .A switch'V of this general type is described in 'detailjinthe patent to Reynolds 2,021,329 of November 19, 1935. Accordingly, each of the primary district switches, such as switch PD-llkisprovided with `ilvesel'ect bars,

Veach serving two separate horizontal rows o1' contacts, Yand tenselect'magnets. such as the magnets I'ZI, I22-and I23,fth e magnets being associated with the bars in pairs, one magnet for rotating the bar in one direction and the other magnet of the pair for rotating the same bar in the other direction. The switch is also equipped with ten vertical bars, one for each of. the ten vertical rows of contacts and corresponding operating magnets, such as magnets |24, |25 and |26. The select magnets of any one of the primary district switches are separately and selectively energized by suitable circuit means to prepare the corresponding select bar by rotating it to its set position.

While the select bars of any one of the primary switches are operable separately from the bars of the other switches as above described, the select bars of the remaining switches` at the switching state, such as the secondary district switches and the office primary and secondary switches, are mechanically joined so that a plurality of them are operated simultaneously by common means. For instance, the district sec--l ondary switch SD-- has ve select bars, three of which are illustrated. The bar |21 serves two horizontal rows of contacts, the No. 0 and No. 1 rows. The bar |28 serves two rows of contacts, such as the No. 4 and No. 5 rows. Likewise the bar |29 serves two rows, such as the No. 8 and No. 9 rows. Each of the other nine secondary district switches is also provided with five select bars, the corresponding bars |39, |3|, and |32 of. switch SD-ll and bars E33, |34, and |35 of switch SD-S being shown. The bars serving the No. 0 and No. 1 rows of contacts of all ten switches, including the bars |21, |30, and |33, are mechanically joined by an operating rod |38. The rod |36 is connected to the respective select bars by levers as illustrated and at its lower end is coupled to an armature which is controlled by two select magnets |31 and |38. One of these magnets when energized moves the bar |36 longitudinally in one direction and rotates all of the individual select bars to prepare the contacts in the No. '0 rows of all ten switches. The other magnet when energized moves the rod |36 in the opposite direction and rotates the individual select bars in the other direction to prepare the contacts in the No. 1 rows of the switches. In like manner four other operating rods, including rods |39 and |49, are provided for operating the.

remainingr four sets of ten select bars. In a similar manner the ten primary ofce selectors PO-D to PO-S are provided with five operating rods, three of which, rods |4|, |42 and |43, are shown. The rod |4| operates the individual select bars |44, |45, |46, etc. for preparing the contacts of the No. O and No. 1 rows of. the corresponding switches. The rod |42 controls the individual select bars associated with the No. 3 and No. 4 rows of contacts, and the rod |43 controls the individual select bars assigned to the No. 8 and No. 9 rows of contacts. In the same manner the secondary ofce selectors are provided with five operating rods, including the rods |41, |48, and |49. These rods control the correspondingindividual select bars of the ten switches in the manner already described in connection with the district secondary and cnice primary selectors.

It has been suggested for the purpose of illustration that the district and oice frames comprise ten primary switches and ten secondary switches per frame. It should be understood, however, that any suitable number of primary and secondary switches may be provided and that the invention is not limited to any particular number of switches. Furthermore, the capacity of the individual switches may be selected in accordance with the requirements of the system. It is convenient to describe the system in connection with switches having ten rows of contacts in each direction. In some cases, however, it would be desirable to use switches having other capacities, such as those having twenty rows of contacts.

In order to establish a connection through the switches illustrated in Figs. 1 and 2, digit recording and controlling mechanisms are provided which register the designations representing the `wanted connections to subscribers lines and which utilize these designations to determine the proper trunk groups to be used, and to determine the proper links that must be tested and utilized to establish the connection to the chosen idle trunk in the group. One of. these mechanisms, which are known as markers, is illustrated brieiiy in Fig. 3 of the drawings. When a call is received and the designation has been established in the marker, connecting devices, known as frame connectors, are operated to establish connections between the marker and the switches of the district and oflice frames which are to be used in establishing connections. 'I'hese frame connecting devices are also illustrated briey in the lower part of Figs. 1 and 2. For a full and detailed disclosure of a cross-bar system of this general class in which switch controlling markers serve to control the selecting switches to establish the desired connections, reference is made to the copending application of W. W. Carpenter Serial No. 27,305, led June 19, 1935, granted as Patent 2,093,117, September 14, 1937.

A description will now be given of the operation of the system. Since calls incoming to the district frame appear at random on the district trunks leading to the ten diiferent primary switches, and since an idle outgoing trunk that may subsequently be found in the desired group outgoing from the oice frame may have its appearance in any one of the oflice secondary switches, it is necessary that the marker have information concerning the location of both the calling district trunk and the selected idle outgoing trunk before it can proceed to test the link paths interconnecting these two trunks and to operate the switches to complete the connection. If, for example, the call appears in the group of ten districttrunks IUD, all of which lead to the primary district switch PD-, the connection must be extended over some one of the ten links |2. And in order that the marker may test the links ||2 to the exclusion of other groups of links, such as groups H3, H4, etc., the test leads from the marker are selectively connected to the group l2 by connecting means 59. Since the ten links |2 extend respectively to the ten district secondary switches, it is possible for the connection to be completed through any one of these secondary switches, provided the corresponding link in the group l2 is idle and there is an idle link outgoing from the secondary switch in the proper direction. The group of links or office trunks H5, H6, ||1, etc. outgoing from the district secondary switches to the proper office frame appear respectively in the oceprimary switches, as explained, and any one of these trunks may be used for the connection, provided it is idle and provided the office primary switch in which it terminates has an idle link extending to the particular oice secondary switch in which the determined idle trunk appears. From what has been said it will be seen that the particular one of the district secondary switches to be used for the connection is not known until the district links, the oflice trunks, and the oiiice links have been tested. However, as soon as the position of the calling district is determined the number of the horizontal row of contacts in -the district secondary switches through which the connection would beextended is known.

to say,4 the connection will be completed through either one of the No. 0 to the No. V9 horizontal rows in the secondary district switches accord- VPD-0 to PD--9. For this reason it is possible Ving tol-whether the calling district trunk appears in thecorresponding primary district switches itis possible to operate atthe beginning the proper one of the common operatingrods |4I |42, and 143 to prepare all ten of the primary office switches.V Again theexactlocation of the idle outgoing trunk inthe group is not known until the trunks have been tested. It 'may be found on any one of the secondary office switches SO-0 to SO9.V But the horizontal Yrow location. of the "trunk group is known as soon as the group is identified. VFor this reason it is possible Vto proceed at once to operate the properV operating rods |41, |48,V |09l to prepare all tenof the'secondary switches for extendingthe connection toany one of the trunks in the desired group that may subsequently be foundidle when the test is made.

AssumeV that the" call Vappears on trunk |5| in 'the group ,|00 appearing in primary district When the call appears on theV trunk |5| theindividual select 'magnet |2| YisV operated to lprepare the switch. Also the appearance of the call causes the operationY of a connecting relay |755 which isrindividual to the primary switch PD-0.

tively. Also relays |52-, |53 and |54, individual respectively to primarydistrict switches IPD-I, PD-5 and PD-9 are illustrated.V In a similar manner relays are provided forthe remaining' primary district YswitchesfPDL-Z, PD'-3; PD-6 and PD1. The purpose of these relays is to closecircuits for selectively operating the rods |36, |30, |40,V`etc. to position the! selectbars'of the secondary district switches. Relay |55 in operating closes the circuit for themagnet |31.

The-magnet |31 attracts its 'armature and moves the rod |36 longitudinallyto rotate the select bars |21,Y |30, |33, etc., to prepare the contacts in the horizontal No. 0 krows ofv all secondary switches SD-0 to SD-Y-S. Y Y

Aslsoon as therwanted designation has been received. andrecorded, an idle marker, `such as the one illustrated in Fig. 3, is takenin use,

and the wanteddesignation is transferred there-V 'I'he marker analyzes the designation andV determines the desiredY outgoing Vtrunk group. Assumegfor example, thatthe trunk group over which the connection must be extended includesY the trunks |08, |04, |05, etc;, appearing in the No. 0. horizontalrows ofthe oflicesecondaryswitches. Itiisnow ,known .thatA theconnection must be ex- That is V tacts inthe switches. Yis located in other horizontal rows of contacts in the switches, the marker causes the operation of the proper one of therelays, such as relays |10,

Relays |56 Vand VI 51V areV individual to switches PD-4'and PD--8, respectended overthe No. 0 horizontal row of some one of the ten. oiiice secondary switches SO-0 to SO-9. Accordingly, the marker may now proceed to cause theoperation of the common operating rod: |141. To do this a circuitv is closed from one of the relays |63,|64, etc., to operate ythe relay I.65. The relay is individual to the zero horizontalv rows of contacts in the secondary switches, and in operating it closes a circuit for themagnetY |86. The magnet |66 operates the rod |41 Yto-rotate the individual select bars-|61, |68, |69, etc., to prepare the No. 0 rows-of con- If the desired trunk group |1|, |12, etc., to rotate the corresponding select bars. j v Y,

The marker connects itself to the wanted group of trunks. through the frame connector shownat f the bottom of' Fig. 2. To do this the relay |58 individual to the marker is operated, and the relay |59 individual to the trunk group is operated. TheV test leads |60 are thus extended through to the test conductors ofthe trunks of the group. i

These trunks are tested'bymeans of the test rei laysll, |62,etc., and an idle one of the trunks is found. Assume that trunk |03 is idle and is selected for use for extending the connection.V Y Since the trunk |03fappears in the switch SO'-0,

it is now evident that the'connection must be completed throughrthe No. 0 level of some one of the ten-cnice primary switches PO-0 to PO-8. s Accordingly, the marker causes the operation ofthe common operating rod |4| to position the select hars |44', |45, |46 associated with the No. 0 rows of contacts in the switches. To accomplishthis the-marker closes a circuit'over the front contact of one of the relays |13, |14', etc., to cause the energization of the relay |19 which is individual to the zerohorizontal rows of contacts. Relay |-19 operates the magnet |16 which in turn actuates Vtherrod |4I. Other relays |15, |11, etc., 1ndividual Vto other rows of contacts in the primary ofce switches, are illustrated.V s

VThe select bars of'rall switches that can participate in the completiony of the desired connection have now been operated, and the'system is ready to make a test ofthe various link paths extendingv from the'calling district trunk |5| to the 'idle outgoing trunk |03.

These link paths are tested' bythe relay sets |80, |8`|, |82 in the marker. There are ten test relays in the set |80, and these are connected through a connecting mechanism |50 to the'ten respective links-in the group ||2. The ten test'relays inthe set 18| are connected through the connecting mechanism |83 to the respective ten oiiice trunks inthe group, including trunks H5, ||6 and ||1. In like manner the ten test relays in the set |82 are connected' through 3 the mechanism |84 to the ten links, including links |85, |86, and |81, which appear in the No. 0 horizontal rows of the primary office switches and trunk |03'. The idle paths are indicated by the non-operated condition of all three of the corresponding test relays in thesets |80, |8| and |82. For example, if the first path through the switches is idle, includingthe link |878, the trunk |5,v and. the link. |85, all three test relays |88,

|90, |93 remain deenergized.y Finding this idle path through the switches, the marker proceeds to cause the operation of the hold magnet |24 which isindividual to the link |88 inthe primary disvwhich extend tothe vertical rows of contacts in Vthe secondary office switch SO-0 reaching the trict switch PD-ll, the hold magnet |92 which is individual to the trunk I5 in the secondary district switch SD-, the hold magnet |93 which is individual to the trunk ||5 in the primary oiiice switch PO-|J, and the hold magnet 94 individual to the link in the secondary oiice switch SO-U.

The operation of these hold magnets completes the establishment of the connection through the switches, and the select magnets may now be released. Also the other operated equipment may be restored to normal, and the connection is held in any well-known manner under control of equipment individual to the talking circuits. When the common operating magnets |31, V56 and |65 have released, thev corresponding operating rods |36, |4| and |41 permit the individual select bars of the several cross-bar switches to restore to their neutral positions. These switches are now free to be seized by another marker for the establishment of another connection from an incoming district trunk to an outgoing trunk on the office frame. For a more detailed description of the manner in which connections are extended through switches of this kind under the control of a marker and associated equipment reference is made to the above-mentioned application of W. W. Carpenter, Serial No. 27,305, filed June 19, 1935, granted as Patent 2,093,117, September 14, 1937.

It Will be noted that the time required for eX- tending a connection through the district and office frames is extremely small. And during this interval only one marker can be associated with the district and office switches. For this reason it is possible to operate select bars of all of the switches, as has been explained herein, to prepare them for the establishment of the connection. And since it is not known at the beginning which switches will be called upon to complete the connection, it is desirable, and it simpliiles the circuits to a great extent, to be able t-o prepare all switches which can possibly take part in the connection prior to the actual determination of the particular switches that are to be used.

What is claimed is:

1. In combination, a switching stage comprising a plurality of cross-bar switches, circuits incoming to said switches, a group of circuits outgoing from said stage, each of said switches having one o-f said outgoing circuits appearing therein, each of said switches having a cross-bar for the particular one of said outgoing circuits therein and serving to eiect connections between the incoming circuits and said particular outgoing circuit, and a common driving device for operating simultaneously all of the cross-bars of said switches which serve the circuits of said outgoing group.

2. In combination, a switching stage comprising a plurality of cross-bar switches, circuits incoming to said switches, a group of circuits outgoing from said stage, each of said switches having one of said outgoing circuits appearing therein, each of said switches having a select bar for the particular one of said outgoing circuits therein, a common operating device mechanically coupled to all of the select bars of said switches which serve the circuits of said outgoing group, and means for energizing said operating device to position all of the select bars to which it is coupled.

3. In combination, a switching stage comprising a plurality of cross-bar switches, circuits incoming to said switches, a group of circuits out- Vgoing from said stage, each of said switches having one of said outgoing circuits appearing therein, each of said switches having a select bar for the particular one of said outgoing circuits therein, a common operating device mechanically coupled to all of the select bars of said switches which serve the circuits of'said outgoing group, means for energizing said operating device to position all the select lbars coupled thereto to prepare all of the corresponding switches for the establishment of a connection to said group of outgoing circuits, and further means for operating a particular one of the prepared switches to complete the establishment therethrough of the connection to the corresponding one of the circuits of the outgoing group.

4. The combination in a switching stage of a plurality of cross-bar switches having rows of contacts, circuits incoming to said stage, a group of trunks outgoing from said stage and distributed among said switches, each outgoing trunk appearing in a contact row of some one of said switches, select bars for said switches, each select bar serving to prepare a particular row of contacts for operation, a common actuating mechanism coupled to all select bars serving the contact rows in which said trunks appear, means for operating said mechanism to position said select bars, operate bars for said switches cooperating with the select bars to close said contacts, and means for actuating an operate bar of some one of said switches 4to close the contacts of the row prepared by the positioned select bar and establish a connection from an incoming circuit to the corresponding trunk of said group.

5. The combination in a switching stage of a plurality of cross-bar switches having rows of contacts, circuits incoming to said stage, a group of trunks outgoing from said stage and distributed among said switches, each outgoing trunk appearing in a contact row of some one of said switches, select bars for said switches, each select bar serving to prepare a particular row of contacts for operation, a common actuating mechanism coupled to all select bars serving the Contact rows in which said trunks appear, means for operating said mechanism to position said select bars, operate bars for said switches cooperating with the select bars to close said contacts, means for testing the trunks of said group to determine an idle one, and means for actuating an operate bar in the particular switch in which appears the idle trunk to establish a connection from an incoming circuit to said idle trunk.

6. The combination in a switching stage of a plurality of cross-bar switches, .a plurality of sets of select bars, each set including a bar in each of the several switches, mechanical means for linking together all bars in each set, circuits appearing in said stage, there being one circuit for each of the several select bars, operating devices for said sets of bars, means for operating any one of said devices to position all bars of the corresponding set, and means cooperating with any one of the select bars of the positioned set for establishing a connection through the corresponding switch with the corresponding one oi' said circuits.

'7. The combination in a switching stage of a plurality of cross-bar switches, a plurality oi sets of select bars, each set including a bar in each of the several switches, mechanical means for linking together all bars in each set, trunks outgoing from said stage, there being one trunk for each of the several .select bars, operating devices for fsaid sets of bars, means for operating any one of 'said devicesf to position .all liars oftheV corre sponding set, operate `bars' .for eachY .of said fsw'itches, means forv selectively operating an operfate bar of` anyone of said switches to coact with `the positioned select bar to' establish a connection'ito'the 4particular trunk associated with said sele'ctbar.` Y 8; The combinationin switch; af'plurality of 'trunks arranged impairs, -each pairbeing served'by a differentone of said bars; -a common operating l device mechanically 'coupled to alluofrsaidV bars, means for ,casing -said device to position all of said bars'to select Y one or the other of the trunks of each of the re'- 'spective pairs, andrmeans gcooperating with the 'positioned bar ofianyone of saidrswitches 'to a switching stageof 9.V iph'iraiityY ofrswitches, select bar's, one Yfor each:

v2,110546()Y y Y effect connection withthe corresponding one o! the trunks, Y Y Y 9. The combination in a switching stage of a pluralityrrof switches,*selectbars, one for each switch a plurality of Vtrunks arranged in pairs, s

each pair; being served by a `different one of said bars, a common operatingA device mechanically coupled to all' of said bars, means for rendering said device effectivet'orotatefall of said bars in i one direction to select oneof the trunksof each f ofthe respective pairs and effective to rotate all of said bars in theV opposite direction to select theother trunk of each of the respective pairs.

and means cooperating with the rotatedbariot f any one of said switches to effect connection with the corresponding one of the trunks.

Y WARREN W. CARPENTER.' JOHN N. REYNOLDS. 

